The present invention relates, in general, to lighting devices. More particularly, the present invention pertains to an asymmetric lamp, having an improved reflector assembly, that provides a better quality of light for a user.
Generally, asymmetric lamps, such as desk lamps or table lamps, which are designed to provide illumination for a work area should:
(a) uniformly illuminate the work area, such as an area approximately 11 inches wide by approximately 17 inches long; PA0 (b) gradually reduce the light level from the work area to surrounding areas, including areas toward, under, and behind the lamp; PA0 (c) be operable from a position away from the work area to leave the illuminated work area clear and the user's movements unrestricted; PA0 (d) project light at a suitable angle onto the work area; PA0 (e) emit light below normal eye level, which, on the average, is about 40 centimeters above the plane of the work area; PA0 (f) prevent glare; and PA0 (g) be aesthetically pleasing in appearance.
However, designing a lamp that can satisfy the above criteria and be economically produced is difficult. In practice, many design trade-offs must be made in order to manufacture an acceptable product.
Lamps that provide even lighting for a work area are known. For instance, U.S. Pat. No. 4,298,921 to Krogsrud et al. describes such a lamp. The lamp disclosed in this patent includes a reflector assembly with a plurality of facets.
Asymmetric lamps with curved reflectors have been suggested. For example, an asymmetric lamp having a hyperbolic reflector has been proposed. However, manufacturing a reflector that follows a smooth hyperbolic curve is difficult. Such a hyperbolic reflector is hard to fabricate economically inasmuch as tight tolerances must be maintained. Moreover, such a hyperbolic reflector typically includes surface irregularities, e.g., indentations and protrusions. These surface irregularities cause the light from the hyperbolic reflector to be nonuniform. That is, these surface irregularities produce discontinuities or striations in the light. The discontinuities in the light may be annoying to a user, especially if the lamp is vibrating, for instance, due to the operation of a typewriter or a printer. In an attempt to overcome the problem with discontinuities and striations, a generally hyperbolic reflector formed from a number of rectangular surfaces or facets has been produced. A Luxo PL-410 lamp made by Jac. Jacobsen A.S includes such a reflector. Although such a reflector has reduced the magnitude of the problem, such a reflector has not eliminated the problem.
Accordingly, a need exists for an inexpensive asymmetric lamp having a reflector assembly that provides uniform light without discontinuities and striations, and otherwise satisfies the criteria listed previously.